Soil mineral mapping using operational remote hyperspectral sensing  

Authors / CoAuthors

Cudahy, T. | Jones, M. | Thomas, M. | Caccetta, M. | Hewson, R.

Abstract

A fundamental component of soils is its mineralogy which is a key driver/indicator of important soil properties/processes such as soil pH (acidity), metal availability (e.g. Al, K, Fe, Si, Ca, Mg) and water content/permeability/runoff. However, soil mineralogy is not routinely measured as part of current soil mapping programs at the paddock-, catchment- or continental-scales mainly because currently deployed measurement technologies are not able to deliver soil mineralogy directly, though remote radiometric and microwave sensing technologies do provide useful soil information. In contrast, mineralogy is now being efficiently delivered to the Australian minerals exploration industry through a new generation of field, airborne and spaceborne hyperspectral technologies (www.hyvista.com; nvcl.csiro.au/). This mineral information includes two of the three major soil mineral components, namely: clays (e.g. kaolinite, illite, smectite); and iron/aluminium oxyhydroxides (e.g. hematite. goethite, gibbsite), with specific information being delivered on their composition, abundances and physicochemistries (disorder and chemistry). The third dominant soil mineral component, quartz, is also spectrally measurable but has diagnostic features at wavelengths longer than current "operational" hyperspectral systems. These hyperspectral technologies thus provide an excellent opportunity to transfer mineral mapping capabilities being developed for the minerals industry into the soil mapping application, especially for establishing baseline inventories of soil mineral composition and providing a possible mechanism for quantitative monitoring of change in soil properties related to its mineralogy (e.g. pH, soil loss, water effects, metal activities and possibly soil carbon and salinity). This opportunity is explored using results from a collaborative geological remote sensing project between the CSIRO, the Geological Survey of Queensland and Geoscience Australia (www.em.csiro.au/NGMM, www.nrw.qld.gov.au/science/geoscience/projects/hyperspectral.html) which involves the collection and processing of 25,000 km2 of airborne HyMap imagery (~300 flight-lines at 5m pixel resolution and totalling >1 Terabyte of raw data) from across Queensland, including areas covered by airborne radiometrics and published geology at 1:100 000 scale around the Mount Isa region. The processed hyperspectral data show that lateritic materials in the Tick Hill area comprise relatively abundant iron oxides and kaolinite (poorly ordered) whereas the radiometrics shows these areas as being relatively high Th and U counts. This kaolinite is presumably developed in response to more acid conditions and/or better (downward percolating) drainage. The hyperspectral data also maps extensive areas of Al-smectite (montmorillonite) associated with the weathering of carbonate (calcite and dolomite) parent rocks or as "pedogenic" occurrences in alluvium/colluvium, with the latter sometimes associated with abundant opaline silica (also mapped using the hyperspectral data). These Al-rich smectites are formed in more alkaline conditions where there is sufficient Ca or Mg and water at the near surface and typically show in the radiometric as being poor in K and Th. Muscovite (water-poor, K-bearing white mica) is mapped over exposed parent rocks whereas illite (water-rich, K-bearing white mica) is typically mapped in weathered materials, including many soils and dried lake beds where there is sufficient available K. The radiometric data typically shows these areas as being K-rich. Note that the accuracy of the hyperspectral clay mineral maps was also validated by field sampling and associated laboratory spectral and X-Ray diffraction analyses.

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nonGeographicDataset

eCat Id

65488

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Keywords

• External PublicationAbstract

( Theme )

• image processing

( Theme )

• mapping

( Theme )

• soils

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2008-01-01T00:00:00

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Creative Commons Attribution 4.0 International Licence    

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geoscientificInformation

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